Application background: With the continuous development of photovoltaic inverter and UPS technology and the continuous expansion of the market, the requirements for inverter efficiency have been more and more valued by manufacturers, and the three-level topology has emerged as the times require. Compared with the traditional two-level structure, the three-level inverter has the advantages of low voltage stress and loss of power devices, good output waveform quality, and high efficiency. It is a new direction for the development of photovoltaic inverter technology.